Control of Pythium ultimum with S-methoxy- or S-3-methylthiophenyl N-alkylthiolcarbamates

ABSTRACT

Novel S-3-methoxyphenyl N-alkylthiolcarbamates such as 3-methoxyphenyl N-methylthiolcarbamates, and S-3-methylthiophenyl N-alkylthiolcarbamates such as 3-methylthiophenyl N-methylthiolcarbamate are disclosed, which are useful to control the plant pest Pythium ultimum (Damping Off). Also disclosed are the methods of controlling this plant pest with these compounds.

This is a division of application Ser. No. 693,666, filed June 7, 1976,now U.S. Pat. No. 4,056,549.

BACKGROUND OF THE INVENTION

The invention concerns S-substituted phenyl N-alkylthiolcarbamateswherein the substituted phenyl is 3-methoxyphenyl or 3-methylthiophenyl,particularly those in which the alkyl is from one to four carbon atoms.The invention also concerns the control of the plant pest Pythiumultimum.

DESCRIPTION OF THE PRIOR ART

Plant pests, such as the fungus of Pythium ultimum, continually affectthe growth of crops, trees, and other desirable vegetation. One methodof controlling plant pests such as fungi is by application of chemicalswhich affect the fungi. These chemicals are applied to the soil, to thedesirable plant, or directly to the fungi itself. Because thousands ofspecies of fungi exist, which differ in tolerance to chemicals, newchemicals must be discovered which are effective to control thedeleterious effects of particular fungi.

The prior art shows that certain thiolcarbamates are effective againstplant pests. The following patents and references illustrate thedifferent thiolcarbamates claimed to be effective against certain plantpests.

U.S. Pat. Nos. 2,977,209 and 3,265,563 disclose S-phenylN-alkylthiolcarbamates, S-chlorophenyl N-alkylthiolcarbamates,S-ethoxyphenyl N-allylthiolcarbamate, S-ethoxyphenylN-alkylthiolcarbamates, S-p-tolyl N-alkylthiolcarbamates, andS-2,4-dimethylphenyl N-alkylthiolcarbamates as herbicides andfungicides. U.S. Pat. No. 3,632,332 disclosesS-4-methylbenzyl-N,N-diethylthiocarbamate as a herbicide for ricefields. U.S. Pat. No. 3,301,885 discloses S-substituted phenyl N-alkyl,N-alkoxythiolcarbamates as herbicides, miticides, and insecticides. U.S.Pat. No. 3,687,653 discloses trifluoromethylbenzylN-alkylthiolcarbamates as herbicides. U.S. Pat. No. 3,046,189 andCanadian Pat. No. 789,575 disclose S-alkyl N-alkylthiocarbamates asnematocides. R. Reimschneider and O. Lorenz, in Monstsch., 84, 518(1953) describe S-phenyl N,N-dimethylthiolcarbamate, and D. G. Crosbyand C. Niemann, Journal of American Chemical Society, 76, 4458 (1954)describe S-phenyl N-cyclohexylthiolcarbamate, and S-phenylN-phenylthiolcarbamate. Netherlands Pat. No. 6,606,753 disclosesS-phenyl N-trifluoromethylphenylthiocarbamate and S-substituted phenylN-substituted trifluoromethylphenylthiocarbamates as anthelmintics. M.S. Newman and H. A. Karnes, Journal of Organic Chemistry, 31, pages3980-3983 describe S-β-naphthyl N,N-dimethylthiolcarbamate,S-2-nitrophenyl N,N-dimethylthiolcarbamate, S-3-nitrophenylN,N-dimethylthiolcarbamate, S-2,4,5-trichlorophenylN,N-dimethylthiolcarbamate, S-3-trifluoromethylphenylN,N-dimethylthiolcarbamate, S-2,3,5,6-tetramethylpentylN,N-dimethylthiolcarbamate, S-4-tertbutylphenylN,N-dimethylthiolcarbamate, S-2-methoxyphenylN,N-dimethylthiolcarbamate, and S-4-methoxyphenylN,N-dimethylthiolcarbamate. U.S. Pat. No. 3,932,632 disclosesinsecticides of dithiophosphate compounds mixed with S-arylN,N-dialkylthiolcarbamates, or S-aryl N,N-dialkylenethiolcarbamates, orS-aryl N,N-dialkynylthiolcarbamates, or S-aryl N,N-(alkyl, alkylene, oralkynyl), (alkyl, alkylene, or alkynyl)thiolcarbamates where the arylmay be a substituted phenyl.

SUMMARY OF THE INVENTION

The invention concerns novel substituted phenylthiolcarbamates of thegeneral formula: ##STR1## wherein: Ar is selected from the groupconsisting of 3-methoxyphenyl and 3-methylthiophenyl; and

R is an alkyl of from one to four carbon atoms.

The invention also concerns the method of controlling the plant pestPythium ultimum.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The S-substituted phenyl N-alkylthiolcarbamates are represented by thegeneral graphic formula: ##STR2## wherein: Ar is a substituted phenyl of3-methoxyphenyl, and 3-methylthiophenyl; and

R is an alkyl of from one to four carbon atoms.

The phrase "an alkyl of from one to four carbon atoms" as used hereinand in the claims refers to:

methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, andtert-butyl.

The novel compounds in which Ar is any of the substituted phenylsmentioned herein, and R is an alkyl of from one to four carbon atomsmentioned herein are:

S-3-methoxyphenyl N-methylthiolcarbamate;

S-3-methoxyphenyl N-ethylthiolcarbamate;

S-3-methoxyphenyl N-n-propylthiolcarbamate;

S-3-methoxyphenyl N-isopropylthiolcarbamate;

S-3-methoxyphenyl N-n-butylthiolcarbamate;

S-3-methoxyphenyl N-sec-butylthiolcarbamate;

S-3-methoxyphenyl N-isobutylthiolcarbamate;

S-3-methoxyphenyl N-tert-butylthiolcarbamate;

S-3-methylthiophenyl N-methylthiolcarbamate;

S-3-methylthiophenyl N-ethylthiolcarbamate;

S-3-methylthiophenyl N-n-propylthiolcarbamate;

S-3-methylthiophenyl N-isopropylthiolcarbamate;

S-3-methylthiophenyl N-n-butylthiolcarbamate;

S-3-methylthiophenyl N-sec-butylthiolcarbamate;

S-3-methylthiophenyl N-isobutylthiolcarbamate; and

S-3-methylthiophenyl N-tert-butylthiolcarbamate.

Of these compounds, those in which R is methyl, ethyl, n-propyl, andisopropyl are preferred, and especially preferred are S-3-methoxyphenylN-methylthiolcarbamate and S-3-methylthiophenyl N-methylthiolcarbamate.

SYNTHESIS OF THE COMPOUNDS A. Synthesis Routes

The compounds may be synthesized by the following routes:

(1) Reaction of substituted phenylthiols of the general formula ArSHwith the appropriate isocyanates of the general formula RNCO, wherein Arand R have the same significance as mentioned hereinbefore.

(2) Reaction of a substituted phenyl thiolchloroformate of the generalformula ##STR3## with an amine of the general formula ##STR4## whereinAr and R have the same significance as defined hereinbefore.

(3) Reaction of a substituted phenylthiol of the general formula ArSHwith a carbamoyl chloride of the general formula ##STR5## wherein Ar andR have the same significance as defined hereinbefore.

b. Synthesis by Reaction of Substituted Phenylthiol and an Isocyanate

The following example illustrates the synthesis of the compounds byreaction of a substituted phenylthiol with the appropriate isocyanate.

EXAMPLE I S-3-methoxyphenyl N-methylthiolcarbamate

Methylisocyanate (2.2 grams, 39 millimoles) in anhydrous ethylether (10milliliters) was slowly added (20 minutes) to a stirred mixture of3-methoxybenzenethiol (5.0 grams, 36 millimoles) and triethylamine (oneto two drops) in anhydrous ethylether (50 milliliters). The clearreaction mixture was refluxed for four hours, and the ethylether solventwas allowed to evaporate off.

A crystalline material (6.9 grams, 95.7 percent yield) was obtained,which was recrystallized from benzene (100 milliliters) to yield 5.4grams of white crystals of S-3-methoxyphenyl N-methylthiolcarbamate. Thecrystals had a melting point of 85.5°-88° Centigrade, and an infraredspectrum with a N--H band at 3280 centimeters⁻¹ and a C═O band at 1650centimeters⁻¹.

Analysis for: C₉ H₁₁ NO₂ S: Calculated: C, 54.80; H, 5.62; N, 7.10.Found: C, 54.89, 54.70; H, 5.39, 5.30; N, 6.93.

Other inert solvents which dissolve the reactants and products and whichare easily removed from the products by evaporation, drying, filtering,or washing, and which have a boiling point appropriate to the reactiontemperature may be used in lieu of ethylether or benzene, such astetrahydrofuran, hexane, and chloroform. The reaction temperature mayvary from 0° C. to the boiling point of the refluxing mixture.Preferably the reaction temperature range is from 0° C. to 80° C.

c. Synthesis By Reaction of Substituted Phenylthiolchloroformates andAlkylamines

The substituted phenylthiolchloroformates are formed from phosgene andthe appropriate substituted phenylthiol. U.S. Pat. No. 3,165,544describes one method of synthesizing these thiolchloroformates.

The following procedure is used to synthesize the compounds disclosedherein by the reaction of the appropriate thiolchloroformate andalkylamine.

A solution containing a substituted phenylthiolchloroformate of thegeneral formula ##STR6## mentioned herein (45 millimoles) e.g.,(3-methylthiobenzenethiolchloroformate) in about 10 milliliters ofethylether is slowly added dropwise over a 20 minute period to avigorously stirred amine solution. The amine solution contains about 100milliliters of water, 100 milliliters of ethylether, 45 millimoles oftriethylamine and about 45 millimoles of an alkylamine of the generalformula ##STR7## mentioned herein, e.g., ethylamine.

The reaction mixture is stirred for an additional half hour at ambienttemperature, and the layers of solution are separated. The aqueous layeris washed once with about 100 milliliters of ethylether, and thisethylether washing and the ethylether layer of the solution arecombined. The combined layers are washed with about 100 milliliters ofaqueous solutions of 10 weight percent sodium hydroxide, and 10 weightpercent hydrochloric acid, respectively, and then dried with anhydroussodium sulfate (Na₂ SO₄).

After filtering off the sodium sulfate, the ethylether solvent isremoved by evaporation, and the impure S-substituted phenylN-alkylthiolcarbamte, e.g., S-3-methylthiophenyl N-ethylthiolcarbamateremaining is recrystallized from an inert solvent such as benzene.

d. Synthesis By Reaction of Substituted Phenylthiols With theAppropriate Carbamoyl Chloride

The following procedure illustrates synthesis of the compounds mentionedherein, by reaction of substituted phenylthiols of the general formulaArSH mentioned herein with the appropriate alkylcarbamoyl chloride ofthe general formula ##STR8## mentioned herein.

A five (5) milliliter anhydrous ethylether solution of fifty (50)millimoles of the appropriate alkylcarbamoyl chloride, e.g.,methylcarbamoyl chloride and a five (5) milliliter anhydrous ethylethersolution of fifty (50) millimoles of triethylamine are simultaneouslyadded over a forty (40) minute period at ambient temperature to astirred forty (40) milliliter anhydrous ethylether solution of fifty(50) millimoles of substituted phenylthiol, e.g.,3-methylthiobenzenethiol. The reaction mixture is stirred and refluxedfor about two (2) to two and one-half (21/2) hours, and is cooled toroom temperature and poured into about 50 milliliters of distilledwater.

The organic layer and aqueous layer are separated from each other. Theaqueous layer is extracted with ethylether and the extracts are combinedwith the organic layer, which is then washed with about one hundred(100) milliliters of a 10 weight percent aqueous solution of sodiumhydroxide, and then washed with about one hundred (100) milliliters of a10 weight percent aqueous solution of hydrochloric acid, respectively,and then dried with sodium sulfate which is then filtered off.

The solvent of ethylether is removed by evaporation, and the impureS-substituted phenyl N-alkylthiolcarbamate, e.g., S-3-methylthiophenylN-methylthiolcarbamate is purified by recrystallization or othertechniques if necessary.

PROPERTIES

The novel compounds disclosed herein are used to control the deleteriouseffects of the fungus Pythium ultimum.

These useful properties are illustrated by the following test.

CONTROL OF Pythium ultimum (Damping Off) TEST PROCEDURE

Oospores suspensions of Pythium ultimum, which have been examined with ahaemocytometer for oospore (plus chlamydospore) numbers per milliliter,were blended at the rate of 1000 oospores per gram of dry sterilizedsoil.

A blend of sterile soil and the test compound (normally added to thesoil as a solution) was also made. The chemically treated soil was mixedwith the Pythium-inoculated soil and thoroughly mixed in a soil blender,and the mixture was equally divided, and one of the divisions was placedinto a container then seeded with sugar beet seeds, water sealed, andplaced in a greenhouse, maintained at 50-75 percent humidity, and70°-80° Fahrenheit, for 2 weeks.

Containers of sterile soil only, sterile soil plus the test compound,and sterile soil plus Pythium inoculum, were also seeded with sugar beetseeds and placed in the greenhouse.

Observations were made for 14 days, and the final observation was madeon the 14th day after preparing the samples.

Disease severity was determined by comparing the actual count of thesurviving plants in Pythium-inoculated soil with the actual count of thesurviving plants in sterile soil.

Control effectiveness of the test compound was determined by comparingthe actual count of surviving plants in the chemically treated soil withthe actual count of surviving plants in the Pythium-inoculated soil.

Each test consisted of at least three replicates.

The control effectiveness is expressed as percent control calculated bythe following formula: ##EQU1##

The amount of test chemical applied is expressed as pounds per acre(lb/A) for 6 inch depth of soil.

The test results for the compounds are shown in Table 1. Column 1 of thetable gives the example number; column 2 gives the test compound whichwas synthesized as disclosed herein unless indicated otherwise; column 3gives the percent control obtained at fifty (50) pounds per acre.

                  TABLE 1                                                         ______________________________________                                        PERCENT CONTROL OF Pythium ultimum                                                                       Percent Control of                                                            Pythium ultimum at                                 Example No.                                                                            Compound Applied  50 Pounds Per Acre                                 ______________________________________                                        II       S-phenyl N-methylthiol-                                                        carbamate.sup.a  0                                                  III      S-3-methoxyphenyl N-methyl-                                                    thiolcarbamate   71                                                 IV       S-4-methoxyphenyl N,N-di-                                                      methylthiolcarbamate.sup.c                                                                     0                                                  V        S-4-methoxyphenyl N-methyl-                                                    thiolcarbamate   0                                                  VI       S-phenyl N,N-dimethylthiol-                                                    carbamate.sup.b  0                                                  ______________________________________                                         .sup.a described in U.S. 2,977,209 and U.S. 3,265,563.                        .sup.b described in U.S. 2,977,209.                                           .sup.c described in Journal of Organic Chemistry, 31, pages 3980-3983.   

APPLICATION a. Suitable Agricultural Formulations

The compounds disclosed herein may themselves be applied directly to thesoil in the vicinity where the deleterious effects of the plant pestsare to be controlled. It is, however, preferable to use suitableagricultural formulations which contain other ingredients which enhanceapplication of the compound. These agricultural formulations willgenerally comprise from 5 percent to 95 percent or more by weight of oneor more S-substituted phenyl N-alkyl, of the general formula: ##STR9##disclosed herein, or mixtures of these compounds, and either from 1percent to 95 percent by weight of an agricultural diluent, or from 1percent to 20 percent by weight of a surface active agent and otheringredients required to produce wettable powders, dusts, solutions,emulsifiable concentrates, granules, and the like, or both.

Wettable powders will contain from 25 to 80 percent active ingredients,from 0.1 percent to 5.0 percent wetters and dispersants with the balanceconsisting of inorganic absorptive diluents.

Since some compounds are solids, others are liquids, and others areviscous materials, they may be dissolved in one or more solvents andthen sprayed upon the absorptive diluents of attapulgite clay, syntheticfine silica, and synthetic calcium and sodium alumino-silicates, orother solid insecticides, or foliar fungicides mentioned herein and thenthe solvent or solvents are evaporated off.

Emulsifiable oils will contain from 20 percent to 97 percent activeingredient, from 3.0 to 10.0 percent of an emulsifying agent, and mayalso contain from 1 percent to 77 percent water-immiscible solvent suchas xylene or alkylated naphthalene.

Granules will contain from 5 percent to 25 percent active ingredients,and may also contain from 1 percent to 20 percent of a surfactantextended upon a granular base such as vermiculite or granularattapulgite. Granules produced by extrusion or tumbling will containlike amounts of active ingredient and surfactant.

b. Combinations With Other Insecticides and Fungicides

For the control of a wider range of crop-pests and diseases it issometimes desirable to combine one or more of the thiolcarbamates of thegeneral formula: ##STR10## with from 0.05 to 4 parts by weight ofinsecticides and fungicides, etc., known to be effective againstcrop-pests and diseases in concentrated premix or during the applicationstep for foliar applications. Examples of other pesticides are: granulescontaining stable metal azide-metal salt formulations disclosed inassignee's copending application entitled AZIDE-METAL SALT FORMULATIONS,Ser. No. 624,357, filed Oct. 21, 1975, containing S-4-methoxyphenylN-2,3-dibromopropylthiolcarbamate, disclosed in assignee's copendingapplication entitled S-p-METHOXYPHENYLN-BIS-2,3-DIBROMOPROPYLTHIOLCARBAMATE, Ser. No. 631,751, filed Nov. 7,1975, or S-4-methoxyphenyl N,N-bis(2,3-dibromopropyl)thiolcarbamatedisclosed in assignee's copending application entitled S-p-METHOXYPHENYLN,N-DIALLYLTHIOLCARBAMATE and S-p-METHOXYPHENYLN,N-BIS(2,3-DIBROMOPROPYL)THIOLCARBAMATE, Ser. No. 631,802, filed Nov.7, 1975, Sevin 1(naphthyl-N-methylcarbamate), Chlorobenzilate (ethyl4,4'-dichlorobenzilate), Guthion(0,0-diethyl-S-[4-oxo-1,2,3-benzotriazin-3(4H)-ylmethyl]phosphorodithioate),Disyston (0,0-diethyl-S-[2-(ethylsulfinyl)ethyl]phosphorodithioate),Maneb (manganous ethylene bisdithiocarbamate), Karathane (mixture of2,4-dinitro-6-octylphenylcrotonate, 2,6-dinitro-4-octylphenylcrotonate,nitrooctylphenols (principally dinitro),4-(1-methylheptyl)2,6-dinitrophenylcrotonate,4-(1-ethylhexyl)2,6-dinitrophenylcrotonate,4-(1-propylpentyl)2,6-dinitrophenylcrotonate,6-(1-methylheptyl)-2,4-dinitrophenylcrotonate,6-(1-ethylhexyl)2,4-dinitrophenylcrotonate, and6-(1-propylpentyl)2,4-dinitrophenylcrotonate), Blasticidin(blasticidin-S-benzylaminobenzensulfonate), Benlate (methyl1-(butylcarbamoyl)-2-benzimidazolecarbamate), or Plantvax(5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxanilide-4,4-dioxide).

In some instances it is also desirable to include special purposeadditives which will inhibit corrosion, reduce foaming, reduce caking,or increase flocculation.

The following example illustrates a suitable emulsifiable concentrateformulation, for dilution in water for spraying plants, particularly,plant foliage or for application to other plant parts as hereinmentioned. In this emulsifiable concentrate formulation, the percentagesare weight percent.

EXAMPLE VII

    ______________________________________                                        Emulsifiable Concentrate Formulations                                         3-methoxyphenyl N-methylthiolcarbamate                                                                  13%                                                 Xylene                    41%                                                 Isophorone                41%                                                 Atlox® 3404*           1%                                                 Atlox® 3403 F*         4%                                                 ______________________________________                                         *Commercial emulsifier for agricultural pesticides manufactured by Atlas      Powder Co., Wilmington, Delaware, and registered with the U.S. Food and       Drug Administration.                                                     

c. Amount of the Compounds Described Herein to Apply

The novel compound described herein when used for a fungicide, tocontrol plant pests, particularly the soil fungus Pythium ultimum(Damping Off), are applied in an amount effective to control this plantpest. This amount is a fungicidal amount, which amount will vary withthe season of the year, the weather, and the severity of the disease.The fungus include those specifically described and shown herein as wellas equivalent species which are biologically related such as those ofthe genus Pythium and are controlled by application of the compounds.

A single compound may be used in the formulation described herein,preferably a plurality of the compounds are used together either in aformulation or by concurrent application, that is applying one or moreof the compounds to the soil itself. In other applications, one or morecompounds may be applied to the soil, and within about 10 days, the samecompound, or one or more different compounds may be applied to the soilso as to effectively control the plant pests.

When used to control the soil fungus Pythium ultimum the novel compoundsmay be applied at rates of from 6 pounds per acre per 6 inch depth ofsoil to as high as 500 pounds per acre per 6 inch depth of soil,depending upon, the application method, e.g., soil incorporation,discing, band, the type of formulation used, the plant species to beprotected, the extent of the soil infestation, local conditions such astemperature, humidity, moisture content of the soil, nature of the soil,e.g., clay, loam, sand, pH, etc.

Those compounds in which R is methyl, ethyl, n-propyl, or isopropyl maybe used at lower rates such as from 6 pounds per acre to 300 pounds peracre, of these compounds those in which R is methyl may be used at lowerrates of 12 pounds per acre to 200 pounds per acre, and those in whichAr is 3-methoxyphenyl are generally used at the lowest rates of 12pounds per acre to 150 pounds per acre while the compoundS-3-methoxyphenyl N-methylthiolcarbamate itself may be used at 12 poundsto 75 pounds per acre per 6 inch depth of soil. Preferably the compoundis applied prior to planting the plants.

The phrase "to effectively control the deleterious effects of plantpest" as used herein and in the claims means that control required toincrease the yield of plants growing in infested areas and treated withthe compound, as compared to non-treated plants. This effective controlmay range from 10 percent to 100 percent control.

The phrase "applying an effective amount" as used herein and in theclaims means applying that amount necessary to attain effective controlby any application technique in which the compound and plant pest arebrought into mutual contact, such as to the foliage of the plant, to thesoil itself, to the fungus itself, or other plant pest. Generally,application to the soil itself is preferred, that is the compound isapplied directly to the soil and disced or plowed, or mixed with thesoil, generally before the plants are planted. It is also possible insome cases to apply the compound to the soil after the plants have beenaffected by the plant pest.

d. Application to Control Other Plant Pests

Although the novel compounds of the general formula ##STR11## are usedto control Pythium ultimum, this does not preclude their use againstother plant pests such as weeds or fungus.

For example, those compounds in which Ar is 3-methoxyphenyl and R is analkyl mentioned herein, can be used at rates from 50 to 500 pounds peracre per 6 inch depth of soil to control the plant pest of the fungusFusarium solani.

While the invention has been described with reference to specificdetails of certain illustrative embodiments, it is not intended that itshall be limited thereby except insofar as such details appear in theaccompanying claims.

I claim:
 1. A method of controlling the deleterious effects of the plantpest Pythium ultimum, which comprises:applying to the soil an effectiveamount which effectively controls the deleterious effects of said plantpest of a compound of the general formula: ##STR12## wherein: Ar isselected from the group consisting of 3-methoxyphenyl and3-methylthiophenyl; and R is an alkyl of from one to four carbon atoms.2. The method of claim 1, wherein R is selected from the groupconsisting of methyl, ethyl, n-propyl, and isopropyl.
 3. The method ofclaim 1, wherein the compound is 3-methoxyphenyl N-methylthiolcarbamate.4. The method of claim 1, wherein the compound is 3-methylthiophenylN-methylthiolcarbamate.